What do you guys know about those magnetic oil pan heaters? Good idea? Bad idea? Places like JC Whitney sell them. I have a short 3 mile commute and was considering one as a way to warm the oil before driving rather than have it freezing from start to finish on my commute. My concerns are that it will over heat the oil during the night, basically cook it up. Does anybody know how hot they get? One said it won't heat oil over 250 degrees - I don't know that I need my oil to be 250 degrees all night every night. Are there any that would just warm it up to around 100 degrees so I will have excellent flow at start-up during the winter?